Unprecedented in 3.6 Million Years: Climate Change Slows Earth’s Rotation

While Earth’s rotation rate naturally fluctuates, the present elongation of the day is closely linked to climate change. According to new research, it is unprecedented over the past several million years.

Mass Redistribution

In theory, the Earth takes 24 hours to complete a full rotation. In reality, this duration tends to vary considerably, influenced notably by the Moon’s gravitational pull, by several deep geophysical processes on the surface and beneath, and also by phenomena occurring in its upper atmosphere.

Global warming is manifested in particular by the accelerated melting of the ice caps, which leads to a significant rise in sea level and a redistribution of the planet’s mass, thereby slowing its rotation and causing the length of days to lengthen by a few milliseconds.

Initially concentrated near the Earth’s axis, this polar ice flows into the oceans, and the “lost” mass extends toward the equator. Like a figure skater turning more slowly on the ice when they extend their arms, the Earth slows down noticeably.

1.33 milliseconds per century

In a study published in the Journal of Geophysical Research: Solid Earth, researchers from the University of Vienna and ETH Zurich estimated that the length of Earth’s day has increased by 1.33 milliseconds per century since the start of the industrial era. This rate is unprecedented for at least 3.6 million years (late Pliocene), according to paleoclimatic data.

“The current lengthening of the day is mainly attributable to human activities,” notes Benedikt Soja, co-author of the new study.

Because of the intensification of climate change, this effect is expected to intensify over the coming decades, with implications for ultra-precise timekeeping technologies (atomic clocks, GPS…) or financial systems.

Previously, researchers had revealed that China’s colossal Three Gorges Dam had caused a redistribution of water masses large enough to slow the rotation of our planet.